Deep Submergence Synergy: Alvin and ABE Explore the Galápagos Rift at 86°W

For over 25 years,hydrothermal vent communities discovered at the Galápagos Rift near 86°W [e.g., Corliss et al., 1979] have provided the foundation of deep-sea vent biology as their study has led to fundamental discoveries of chemoautorophy and novel symbioses in the deep sea [e.g., Cavanaugh et al., 1981]. Since 1979, numerous physiological and geochemical investigations of the Rose Garden vent community [e.g., Hessler et al., 1988] have been made possible through routine access to this deep sea floor site, provided by the deep submergence vehicle Alvin.This research revolutionized our understanding of basic biological and chemical processes in the deep ocean [e.g., Johnson et al., 1988; Edmond et al., 1979]. In May-June 2002, a sea floor sampling and near-bottom mapping program was conducted using R/V Atlantis (AT7-13), the submersible Alvin,and the autonomous underwater vehicle ABE (Autonomous Benthic Explorer) [Yoerger et al., 1998] to explore and study hydrothermal processes along the Galápagos Spreading Center (GSC) between 86°W and 90°W (Figure 1). This 12-day expedition coincided with the 25th anniversary of the discovery of deep-sea hydrothermal vents at the Galápagos Rift (http://www.divediscover.whoi.edu;Expedition 6). It included a planned revisit of the Rose Garden vent field to conduct multidisciplinary timeseries observations and sampling that would represent a quarter-century perspective at this longest-studied,active hydrothermal vent field. The fieldwork resulted in the discovery of important geological,hydrothermal,and biological changes that have occurred at the Rose Garden site.During the first few Alvin dives of the cruise, it was discovered that the well-developed faunal communities last documented 13 years ago at Rose Garden were apparently buried by fresh basaltic sheet flows.Notable was the absence of 14 sea floor markers used for past experiments and 7 stacks of Alvin dive weights observed on dive 2224. On the first Alvin dive (3788),a nascent,lowtemperature hydrothermal vent field (named Rosebud) was discovered at 2470 m depth,which included an array of young vent animal assemblages colonizing cracks within a fresh, glassy basaltic sheet flow located ~300 m northwest of the last known position of the Rose Garden site PAGES 425, 432–433 Deep Submergence Synergy: Alvin and ABE Explore the Galápagos Rift at 86°W